1. Field of the Invention
This invention relates to a method of storing radiation image data. This invention particularly relates to a long-term storage method for image data obtained in a radiation image recording and reproducing system for diagnosis using a stimulable phosphor sheet.
2. Description of the Prior Art
A novel system for recording and reproducing a radiation image by use of a stimulable phosphor is disclosed, for example, in U.S. Pat. Nos. 4,258,264 and 4,276,473, U.S. Pat. No. 4,346,295 (DE-OS No. 29 51 501), and Japanese Unexamined Patent Publication No. 55(1980)-103472. As described in "Shashin Kogyo" (Photographic Industry), Vol. 40, No. 11 (Ser. No. 401), page 122, this system conducts various image processings on an image signal detected from a stimulable phosphor sheet (imaging plate) carrying a radiation image stored therein by scanning the stimulable phosphor sheet with stimulating rays, thereby to obtain a visible image having an improved image quality, particularly a high diagnostic efficiency and accuracy. This system is very useful particularly for medical diagnosis.
In the aforesaid system, image data on the image signal detected from the stimulable phosphor sheet is converted to digital data and, when necessary, the digital data is displayed on a CRT monitor. Also, the digital data is directly used for modulating the scanning light beam in a reproducing apparatus to reproduce a visible image on a light-sensitive material. Alternatively, the digital data is once stored in a recording medium such as a magnetic tape or a magnetic disk, converted to an electric signal for reproducing, and then used for modulating the scanning light beam in the reproducing apparatus as described above. Thereafter, the recording medium carrying the digital data recorded therein is stored for later reproducing of the radiation image.
Namely, the image data once used for diagnosis is stored for later investigation of the past record of the patient and, when necessary, it is used for again reproducing the radiation image. The method wherein the image data is stored in the form recorded in the recording medium such as a magnetic tape (digital file) is advantageous over the method wherein the image data is stored in the form recorded as a finally obtained visible image in a light-sensitive material (film) in that the space required for storage is smaller. Further, in the method of storing the image data in the form recorded in a film, it becomes impossible to reuse the silver contained in the film. Therefore, this method is not suitable from the viewpoint of effective use of resources. Further, in this method, it is not always easy to retrieve the stored image data.
Accordingly, in the aforesaid radiation image recording and reproducing system, the digital data once used should preferably be stored in a recording medium such as a magnetic tape or a magnetic disk (digital file).
However, even in the method of storing the digital data as a digital file, a problem with regard to the space for storage arises when the storage period becomes long and the number of digital files stored increases. Thus, it is desired to minimize the amount of the digital files stored.